This invention relates to improvements in electrodes of the type used for electrochemical detection and measurement of the concentration of ions in solution. More particularly, the invention is directed to an ultrastable, double junction modular reference electrode finding utility in the assay of low level halide concentrations, sulphides, perchlorates, silver, mercury and other heavy metals. Electrodes finding general utility in those areas in which the instant electrodes are useful are known in the prior art. Such electrodes have taken various physical constructions, and for many specific arrangements certain advantages have been claimed. However, each prior art structure has one or more disadvantages or inadequacies, and none has proven completely suitable for its intended use. For example, may of the electrodes utilize internal solutions or compositions which serve as electrically conductive media. The introduction of such solutions has posed procedural and assembly problems. Additionally, the need periodically to replenish or replace the liquid-like or fluid filler composition dictates the provision of practical access means or sealable ports. A related desirable capability is the ease of disassembly and reassembly of the entire structure for cleaning and for such part replacement as may be desirable or necessary.
Still another important goal of electrodes of the type to which the instant invention is directed is to achieve a minimum of diffusion or escape of the fluid contents from the interior of the electrode proper, thereby to insure reproducibility of results and electrode stability. The extensive investigative and research work carried out in this field, notwithstanding, no electrode developed has been found to be completely satisfactory in all respects. It is, therefore, the aim of the present invention to provide an improved double junction reference electrode which constitutes a structural combination obviating many of the shortcomings of the prior art devices and enabling the realization of advantages and reproduceability in use not heretofore achievable.